Oxygen bleaching agents have become an important alternative to chlorine or bromine bleaching agents in automatic dishwashing formulations. However, many oxygen bleaches are insufficiently stable to be incorporated in surfactant containing detergent solutions. One solution to the instability problem is to encapsulate the agent.
Paraffin wax has been successfully used to encapsulate solid core materials which are unstable in humid or liquid environments (See Lang et al. U.S. Pat. No. 5,200,236 and Kamel et al. U.S. Pat. No. 5,258,132.). The paraffin wax coatings require a specific melting point range and solids content so that the particles sufficiently melt within the washing cycle of an automatic dishwasher to provide effective cleaning without leaving a waxy residue upon cleaned dishware surfaces.
For effective release of the bleach in the wash, it is critical that the oxygen agent has a rapid dissolution rate. It has been observed that oxygen agents, such as phthalimidoperhexanoic acid (PAP), encapsulated in a paraffin wax coating have a dissolution rate slower than useful for incorporation in detergent compositions. The coating material dissolves at washing temperatures but has a tendency to stick to the active core material to inhibit its dissolution rate.